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Thu, 5 Nov 2026 17:49:40 +0000 (GMT) Received: from [9.68.10.150] (unknown [9.68.10.150]) by smtpav04.dal12v.mail.ibm.com (Postfix) with ESMTP; Thu, 5 Nov 2026 17:49:40 +0000 (GMT) Message-ID: <27596ddc-6624-49b3-9ea9-891f477eee38@linux.ibm.com> Date: Thu, 5 Nov 2026 18:49:27 +0100 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 03/20] coverage: add a common debugfs interface To: Sasha Levin , linux-kernel@vger.kernel.org Cc: Alexander Potapenko , Andrey Konovalov , Chuck Wolber , Dmitry Vyukov , kasan-dev@googlegroups.com, Marco Elver , Masami Hiramatsu , Peter Zijlstra , Thomas Gleixner References: <20261103015238.3780910-1-sashal@kernel.org> <20261103015238.3780910-4-sashal@kernel.org> From: Peter Oberparleiter Content-Language: en-US In-Reply-To: <20261103015238.3780910-4-sashal@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-GUID: RcXFwb46gS1f6C_-4ejZWtGccweOzR06 X-Proofpoint-ORIG-GUID: cdZUO34zU9lIS0Rg5-KzPuKetpYscTUl X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYxMTA1MDA3MCBTYWx0ZWRfX0LO84vh4UpoP wmuGlVKJaMHOqNMkG2gLGwIz8QZSilJhE36nVGX/69wROvPdeZXye3clJlr6eN4IUwl8faO3FRd oM5QtdUScaRDx5kiW0O8Ok2IA7jXNMX34VbyPloBLKQFPDHcAIkGe4lJV7VqbngW2mKfXpQ9vgx /yWsoKxxTzIQnYPHL6sioarsHlUTM67KMUTydyABBurgVkP3pgl25FilE+bBhaBlawaoTY6XZKr PZeFJZaGMXVh3V0nDtkJVGTMci+WNSd9+Qz8oC3AZm3/WzIWcolF2bacbfyjNRPBJ2NbDaSxOto WoOHazIgAVRPsJFpsMNpEK9gNfMXRXyM5U90L2jOjoQgx9NkBKejLhoJRGR7OWXvpDxfbqDtXhk IMH3rFo36pc8c0OI94dzDTypiK3LCIA+YhnSrmDzDK0f+PmAjC4q1HWKksK8ZkkM1/Y8X7MipAA NmM7JbKtFpmsKv0/gcw== X-Proofpoint-Spam-Info: AW1haW4tMjYxMTA1MDA3MCBTYWx0ZWRfX9vyDezRGnwnV mOQ1JHavsMRHuJpgZnjbgcDRk51AXQ3MQ3sfD9hILNsb00DvQnD8eKUYsCWwS2Z6uJbD1Bd+Pl9 n65rj/y4itfW7Zo5RUSg9rn4s74xv4U= X-Authority-Analysis: v=2.4 cv=FIqOVOos c=1 sm=1 tr=0 ts=6aecc1b8 cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=IkcTkHD0fZMA:10 a=zJRp6_cAMcgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=uAbxVGIbfxUO_5tXvNgY:22 a=E5mLeVgb6EEcHXiTWj8A:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.138,FMLib:17.12.100.49 definitions=2026-11-05_05,2026-11-04_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 malwarescore=0 impostorscore=0 spamscore=0 lowpriorityscore=0 bulkscore=0 suspectscore=0 clxscore=1015 priorityscore=1501 phishscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2610300000 definitions=main-2611050070 On 03.11.2026 02:52, Sasha Levin wrote: > Each coverage implementation creates its own top-level debugfs entry > with its own conventions: /sys/kernel/debug/gcov/ and > /sys/kernel/debug/kcov. Give them a common root, > /sys/kernel/debug/coverage/, which contains: > > backend name of the selected code coverage measurement implementation > reset write to reset all coverage data of that implementation > gcov symlink to ../gcov when gcov is enabled > kcov symlink to ../kcov when KCOV is enabled > > backend and reset are only present when a code coverage measurement > implementation is selected, so a kernel with only KCOV just has the kcov > symlink. The data formats are defined by the respective toolchains and > stay implementation specific. The existing paths are kept as they are, > since lcov, distribution tooling and syzkaller rely on them; the gcov > reset file now shares its implementation with the common one. > > The common reset never touches KCOV, whose coverage buffers are owned > by the tasks that set them up. This part is slightly inconsistent - there is a common reset attribute, but it doesn't apply to all coverage mechanisms. Also for gcov, there are two reset attributes that perform the same function. Would it make sense to only keep the attribute in the backend directory and possibly mandate a common name via convention? [...] > +void __init coverage_register_backend(const struct coverage_backend *backend) > +{ > + if (WARN_ON(coverage_backend)) > + return; Can this happen at all? -- Peter Oberparleiter Linux on IBM Z Development - IBM Germany R&D